Difficulties in the genetic interpretation of isozyme patterns of Lecithochirium spp. (Trematoda: Digenea)

Abstract.

Isozyme variation in adenosine deaminase (ADA) and glutamate-oxalacetate transaminase (GOT) was examined in 401 individuals of Lecithochirium rufoviride and Lecithochirium fusiforme from Conger conger. The banding patterns obtained for ADA were consistent with a monomeric structure and with single-locus control. This enzyme was polymorphic in the population, with two allozymes being detected. However an additional band, which may correspond to a secondary isozyme, was also observed. In accordance with this interpretation, ADA showed a significant departure from Hardy–Weinberg predictions associated with heterozygote deficiencies. Only one activity zone for GOT was detected in a subset of individuals, whereas some specimens showed a second weakly stained band, which may have been due to host enzyme contamination, although other possible reasons are also discussed. The electrophoretic patterns for ADA and GOT in these species provide examples of how some problems in electrophoretic analysis, such as nonheritable variation, may lead to the misinterpretation of zymograms in systematic and population genetic studies of parasites.